1. Field of the Invention
The invention relates to an arrangement for supplying power to a motor vehicle electrical system by means of a generator and a solar generator.
2. Description of Related Art
Conventionally, the consumers or assemblies connected to the motor vehicle electrical system are supplied with power via a generator and a battery connected downstream of it by means of the engine of the motor vehicle. Furthermore, there are numerous proposals for at least in part adding the current made available by a solar generator to this type of power supply; the solar generator is made, for example, in the form of solar cells which are located preferably on the roof of the motor vehicle. One arrangement for supplying power to a motor vehicle electrical system is known, for example, from German Patent DE 36 04 226 C2. There, a power flow sensor acquires the power flow to or from the motor vehicle battery and supplies it to a control means which adds up the power flow over a given time interval, for example, one day. Depending on whether the total acquired there is positive or negative, the control means opens or closes a switch between the motor vehicle battery and the motor vehicle electrical system to prevent excess discharge of the motor vehicle battery.
Another proposal for use of a solar generator for supplying power to the motor vehicle electrical system is known from published German Patent Application DE 39 24 755 A1. In this known arrangement, the solar generator is connected to the motor vehicle battery via a charge control module. The charge control module controls the charging current depending on the battery temperature. The motor vehicle battery is connected via a switching module to different assemblies or power consumers, specifically the motor of a sliding roof and two fan motors. The switching module is controlled by a control module which acquires the temperature in the motor vehicle interior and the humidity above the sliding roof in order to separate or connect the power consumer from the motor vehicle battery depending on these parameters. Here, the motor vehicle battery acts as a buffer between the solar generator and the power consumers.
The above addressed suggestions for partial power supply of the motor vehicle electrical system by means of a solar generator do not take into account the fact that conversion of power from fossil fuels, such as gasoline and diesel, into electrical current via the generator in motor vehicles is associated with very poor overall efficiency. With consideration of different operating conditions of the motor vehicle, fuel consumption of around 0.5 liter per 100 km per 100 Wh of electricity produced can be expected. This is especially critical in conjunction with motor vehicles which are otherwise optimized with respect to their fuel consumption, for example, the three-liter car which is the goal of the automotive industry.